package com.nulldev.util.web.WebSocketAPI;

import java.net.URI;
import java.util.HashMap;
import java.util.LinkedHashMap;
import java.util.Locale;
import java.util.Map;

import com.nulldev.util.data.Base64.Base64;
import com.nulldev.util.data.FastMath.FastRandom;
import com.nulldev.util.web.URLUtils.URLUtils;

class WebSocketHandshake {
	private static final String WEBSOCKET_VERSION = "13";

	private URI url = null;
	private String protocol = null;
	private String nonce = null;
	private Map<String, String> extraHeaders = null;

	public WebSocketHandshake(URI url, String protocol, Map<String, String> extraHeaders) {
		this.url = url;
		this.protocol = protocol;
		this.extraHeaders = extraHeaders;
		this.nonce = this.createNonce();
	}

	public byte[] getHandshake() {
		String path = url.getPath();
		String query = url.getQuery();
		path += query == null ? "" : "?" + query;
		String host = url.getHost();

		if (url.getPort() != -1) {
			host += ":" + url.getPort();
		}

		LinkedHashMap<String, String> header = new LinkedHashMap<String, String>();
		header.put("Host", host);
		header.put("Upgrade", "websocket");
		header.put("Connection", "Upgrade");
		header.put("Sec-WebSocket-Version", WEBSOCKET_VERSION);
		header.put("Sec-WebSocket-Key", this.nonce);
		header.put("User-Agent", URLUtils.STANDARD_USERAGENT);

		if (this.protocol != null) {
			header.put("Sec-WebSocket-Protocol", this.protocol);
		}

		if (this.extraHeaders != null) {
			for (String fieldName : this.extraHeaders.keySet()) {
				// Only checks for Field names with the exact same text,
				// but according to RFC 2616 (HTTP) field names are case-insensitive.
				if (!header.containsKey(fieldName)) {
					header.put(fieldName, this.extraHeaders.get(fieldName));
				}
			}
		}

		String handshake = "GET " + path + " HTTP/1.1\r\n";
		handshake += this.generateHeader(header);
		handshake += "\r\n";

		byte[] handshakeBytes = new byte[handshake.getBytes().length];
		System.arraycopy(handshake.getBytes(), 0, handshakeBytes, 0, handshake.getBytes().length);

		return handshakeBytes;
	}

	private String generateHeader(LinkedHashMap<String, String> headers) {
		String header = new String();
		for (String fieldName : headers.keySet()) {
			header += fieldName + ": " + headers.get(fieldName) + "\r\n";
		}
		return header;
	}

	private final FastRandom fr = new FastRandom();

	private String createNonce() {
//        byte[] nonce = new byte[16];
//        for (int i = 0; i < 16; i++) {
//            nonce[i] = (byte) rand(0, 255);
//        }
		return Base64.encodeBase64String(fr.bytes(16));
	}

	public void verifyServerStatusLine(String statusLine) {
		int statusCode = Integer.valueOf(statusLine.substring(9, 12));

		if (statusCode == 407) {
			throw new WebSocketException("connection failed: proxy authentication not supported");
		} else if (statusCode == 404) {
			throw new WebSocketException("connection failed: 404 not found");
		} else if (statusCode != 101) {
			throw new WebSocketException("connection failed: unknown status code " + statusCode);
		}
	}

	public void verifyServerHandshakeHeaders(final HashMap<String, String> headers) {
		if (!headers.get("upgrade").toLowerCase(Locale.US).equals("websocket")) {
			throw new WebSocketException("connection failed: missing header field in server handshake: Upgrade");
		} else if (!headers.get("connection").toLowerCase(Locale.US).equals("upgrade")) {
			throw new WebSocketException("connection failed: missing header field in server handshake: Connection");
		}
	}
}
